1
00:00:01,120 --> 00:00:09,350
So exit out of the telnet session from rotas 3 12:56 to rock history and we can see some translations

2
00:00:09,350 --> 00:00:16,250
taking place show IP net translation we can see are two not translations on the table which will time

3
00:00:16,250 --> 00:00:24,330
out after a period of time wrote A or say exit of the telnet session.

4
00:00:26,350 --> 00:00:31,230
Currently we've got those two net translation increase.

5
00:00:31,290 --> 00:00:34,190
Let's do a why shock capture.

6
00:00:34,310 --> 00:00:40,990
So I'm going to capture on the outside interface and in this case let's look at what's arriving at rodders

7
00:00:40,990 --> 00:00:41,850
3.

8
00:00:41,930 --> 00:00:43,640
So what's arriving on that port.

9
00:00:46,860 --> 00:00:58,560
I'm going to full to this for telnet and on router 1 Telenet to rotisserie we can see the telnet data

10
00:00:59,520 --> 00:01:07,580
so some telnet to negotiation taking place and we being prompted for a password.

11
00:01:07,580 --> 00:01:10,940
So we see this in the Why Shock capture.

12
00:01:13,060 --> 00:01:22,860
What I'll do is Antropov sort of Siska and log in and you can see see I see oh there's the Cisco loggin

13
00:01:22,920 --> 00:01:23,970
password.

14
00:01:24,330 --> 00:01:32,090
But what's important to notice is the traffic is coming from a source of 8 to 1 1 1 going to 8 1 1 2.

15
00:01:32,310 --> 00:01:38,220
So it looks like all appears like the traffic is coming from this host going to this host.

16
00:01:38,610 --> 00:01:42,940
Whereas in actual fact the traffic is coming from our one.

17
00:01:43,140 --> 00:01:50,620
But in the wide shot capture we can see that all the communication is between 8 1 1 2 and 8 1 1 1.

18
00:01:50,640 --> 00:01:56,760
So in this example the rotatory prompt is being sent from rotatory to Route 1.

19
00:01:56,930 --> 00:02:05,480
Let's stop that capture and have a look at it on the site so I'll have a look at it on the switch.

20
00:02:06,370 --> 00:02:08,640
So on this part of the network here

21
00:02:12,000 --> 00:02:20,130
we'll do a full telnet once again and I'll exit out of the telnet session notice this was still part

22
00:02:20,130 --> 00:02:21,960
of the same telnet session.

23
00:02:21,960 --> 00:02:32,380
But notice now the address is from 10 1 1 1 2 8 1 1 2 his e x y t

24
00:02:36,730 --> 00:02:40,040
and then we have the session closed.

25
00:02:40,050 --> 00:02:48,390
So in this example the traffic is from this IP address as the source to this IP address as the destination.

26
00:02:48,390 --> 00:02:52,450
But when it's on this interface it's changed to a 2 1 1 1.

27
00:02:52,500 --> 00:02:55,430
So that's an example of that in real time.

28
00:02:55,650 --> 00:03:02,440
Let's do it with two devices.

29
00:03:02,600 --> 00:03:08,240
I'll do the caption now on the side but have to telnet sessions going at the same time.

30
00:03:10,940 --> 00:03:22,580
So telnet wrote a one telnet to the rotisserie and router for telnet to rotisserie.

31
00:03:22,640 --> 00:03:24,090
No it isn't all the output.

32
00:03:24,100 --> 00:03:29,110
You only see 8 1 1 1 communicating with 8 1 1 2.

33
00:03:29,110 --> 00:03:37,810
You don't see that the communication is actually from Rotto 1 and rockfall in all the output it looks

34
00:03:37,810 --> 00:03:41,030
like it's the same two devices communicating with each other.

35
00:03:43,480 --> 00:03:50,870
Whereas in actual fact there are multiple devices communicating here and not just a single source device

36
00:03:50,870 --> 00:03:53,480
talking to a single destination device.

37
00:03:53,480 --> 00:03:55,990
Now you can see that by looking at the port numbers.

38
00:03:56,000 --> 00:04:01,170
So for this session the port number is 1 9 2 0 7.

39
00:04:01,300 --> 00:04:05,270
That's part of the same session 1 9 2 0 7.

40
00:04:05,710 --> 00:04:13,920
But notice here it's a different session number 3 2 4 5 7 3 2 4 5 7.

41
00:04:14,050 --> 00:04:23,380
If we look at the net translations show IP net translation we can see the actual port numbers used by

42
00:04:23,380 --> 00:04:32,610
the devices in the sessions so 3 2 4 5 7 scrolling down 6:41.

43
00:04:33,070 --> 00:04:40,630
So this is the first device 10 one on one and yes the second one 10 1 1 4.

44
00:04:40,710 --> 00:04:45,680
That's once again how the rod is able to differentiate between the devices.

45
00:04:46,730 --> 00:04:53,630
Let's have a look at both output in the show IP translations the best output we can see when it was

46
00:04:53,630 --> 00:04:54,400
created.

47
00:04:54,530 --> 00:04:56,890
So this one was created two minutes and 38 seconds ago.

48
00:04:56,900 --> 00:05:03,350
This one two minutes and 34 seconds ago you can see the use and the timeout and what's left on these

49
00:05:03,350 --> 00:05:04,130
entries.

50
00:05:05,330 --> 00:05:14,120
What's important to remember for dynamic net translations such as this is that multiple internal IP

51
00:05:14,120 --> 00:05:18,010
addresses are being netted to a single external IP address.

52
00:05:18,050 --> 00:05:24,520
You mustn't forget to include the overload keyword.

53
00:05:24,730 --> 00:05:29,870
If you forget to that key word only one device will be able to access the internet.

54
00:05:29,980 --> 00:05:38,320
Overloading enables Pat or port address translation which allows multiple internal devices to share

55
00:05:38,320 --> 00:05:45,850
the same global IP address and the router that's doing the net or in this case port address translational

56
00:05:45,850 --> 00:05:50,080
papped can differentiate between the sessions based on the port numbers.